The present invention relates to methods and apparatus for decorating three dimensional articles such as beverage containers and, more particularly, to heat transfer printing of such containers.
In general, heat transfer printing involves the use of a transfer sheet containing dyes which are sublimatic or meltable. The transfer sheet is made by first printing the dyes in a desired pattern on the transfer sheet, which is usually paper sheet material, in a mirror image of the desired pattern to be applied to the article. Heat transfer printing has previously been utilized primarily for printing on flat articles made of paper, plastic and cloth material. Blake U.S. Reissue Pat. No. 27,892 and Sideman U.S. Pat. No. 3,952,131 are illustrative of prior art heat transfer printing methods, inks and materials.
One type of apparatus commonly employed in heat transfer printing is a heated flat press of the type described in Fitzwater U.S. Pat. No. 4,030,962 in which a flat article, such as a garment, is laid on a flat bed, a printed heat transfer sheet is laid on top of the garment, and a flat plate is lowered onto the paper and garment to apply heat and pressure to effect transfer of the pattern from the transfer sheet to the garment. Then the press is opened to remove the garment and the transfer sheet whereupon a new transfer sheet and garment may then be inserted. Thus, the operation is discontinuous, time consuming, laborious and costly.
Another type of prior art heat transfer printing apparatus is shown by Armstrong U.S. Pat. No. 3,848,435, which employs a heated rotating roller with a continuous roll of transfer sheet material and a continuous roll of fabric material being continuously fed to the printing apparatus in face to face relationship. The apparatus comprises a series of rollers, including a heated roller, against which the transfer sheet and the fabric are pressed by a third sheet-like material referred to as an "endless blanket". The endless blanket is made of any heat resistant material and causes the heat transfer paper and the fabric to be pressed against the periphery of the heated roller with the heat transfer paper engaging the heated roller and the fabric engaging the endless blanket. In order to prevent staining of the endless blanket by portions of the heat transfer paper extending beyond the fabric, those portions may be folded over. In another embodiment, the heat source is a semi-circular array of heat lamps disposed above the outer periphery of the printing roll. It is suggested that the printing roll may be air permeable with a vacuum condition being employed to aid in the transfer of dye vapor to the fabric.
Another type of heat transfer printing apparatus is described in Serex et al. U.S. Pat. No. 4,008,998, in which the fabric to be printed, the heat transfer paper and a heating belt are wound into a composite coil, with heat being supplied by the heating belt. In one form, the heating belt has a series of electro-resistant filaments on tapes and, in another form, a single flat and flexible electrical resistance unit covered by insulating material. The heating belt or the fabric is pre-heated, using heated rollers, prior to being wound into the composite coil, which has an axis parallel to the axes of the feeding rollers, and being further heated by the heating belt. In an alternative form, the fabric and heat transfer paper are coiled and heated by hot air in a roller chamber.
Prior to the present invention, it was known to use individual heat transfer sheets to print flat metallic objects and generally cylindrical objects such as pen or pencil casings or beverage containers by rotably contacting the objects with the sheets. Insofar as is known, however, prior heat transfer processes have not been amenable to the high speed decoration of cylindrical containers. Cylindrical containers have heretofore been decorated by placing a container on a rotating mandrel geared to the rotation of a number of rollers. Each roller deposits a different color and pattern on the container. Due to the inherent problems of registry of the patterns and drying of the colors, the art of decorating cylindrical containers has been severely limited. In particular, process or half-tone printing of detailed images on cylindrical objects has not been obtainable with conventional decorating apparatus, insofar as is known.